1. Field of the Invention
The invention pertains to a switching valve with a valve body separating two working spaces filled with fluid. The valve body has pass-through openings which are covered except for an inlet opening having a cross-section which is controlled by a switching disk as a function of the direction of flow in the switching valve.
2. Description of the Related Art
DE 40 25 115 describes a damping valve with a damping valve body, where elevated damping valve body areas are formed on the base body of the damping valve. These elevated area form valve contact surfaces, through which channels, which are covered by valve disks, extend. At least one ring-shaped valve disk is provided on the valve contact surfaces, which disk has at least one inlet cross-section in alignment with a pass-through channel. The inlet cross-section is covered by a switching disk, which can rise from the valve disk when damping medium from the pass-through channel flows against it in the axial direction of the valve body. This design of a directionally-dependent inlet cross-section, although good in principle, nevertheless suffers from the disadvantage that adhesive forces can cause the switching disk to remain stuck on the valve body. One possible way of counteracting these adhesive effects is to roughen the contact surfaces, either those on the valve body or those on the valve disk. Although experiments have shown this measure does lead to an improvement, the results are still not satisfactory.
U.S. Pat. No. 5,261,448 describes a switching valve with a valve body, which separates two working spaces filled with a fluid from each other, where pass-through openings, which are covered at least partially by a number of valve disks, are provided in the valve body. The open cross-section of the pass-through openings is controlled by a switching disk as a function of the direction of flow. This switching disk has spring sections extending in the circumferential direction, at least one cover surface, and clamping surfaces, which pretension the switching disk against the switching valve outside the cover surfaces and the spring elements, where the minimum of one cover surface is kept in a fixed position with respect to at least one pass-through opening. The limited spring section undergoes deformation in the transverse direction, and thus a low spring rate can be achieved by making the spring section as narrow as possible in the circumferential direction. This, however, in incompatible with the requirement for strength.
The object of the invention is to improve a switching valve with an inlet cross-section, i.e., a switching valve which operates in a directionally dependent manner, in such a way that the smallest possible forces are sufficient to produce the switching movement of the valve elements which release the cross-section of the inlet and also so that the valve is securely closed when pressure is exerted in the opposite direction. The valve is also to be designed so that it operates reliably and has the greatest possible fatigue strength.
The object is accomplished by providing at least one spacer disk between the switching disk and the cross-section of the inlet opening. The spacer disk has at least one opening which communicates with the cross-section of the inlet, the surface area of this opening being larger than the cross-section of the inlet.
The key advantage associated with the use of the spacer disk is that the surface on which the pressure acts to lift the switching disk can be significantly increased without the need to change the size of the cross-section of the inlet opening. The dimensions of the surface on which the pressure acts are completely independent of the cross-section of the inlet opening.
In addition, the switching disk itself can be made of much thicker material, even though the forces which push it open are weaker. As a result, the fatigue strength of the switching disk can be significantly increased.
The large openings in the spacer disk reduce the contact area with the valve disk which must be lifted together with the switching disk from the spacer disk by the incoming flow. This reduction in the contact area also reduces the adhesive forces which can develop. The switching disk can also rest directly on the spacer disk.
So that the openings can have the largest possible cross-sections while at the same time the possibility of a hydraulic short-circuit between the cross-section of the inlet opening and the downstream working space can be avoided, the spacer disk is kept in a fixed position with respect to the cross-section of the inlet opening. The inlet cross-section can be pressed into the valve body or be formed by a valve disk equipped with a gap corresponding to the desired inlet cross-section.
In cases where the switching disk rests directly on the spacer disk, the switching disk is provided with clamping surfaces, which are separated from each other by openings, and with cover surfaces. The cover surfaces have spring sections, which enable them to rise relative to the clamping surfaces. The openings in the spacer disk are aligned with at least one cover surface.
The size of the opening can also be made larger than that of the cover surfaces of the switching disk by providing the spacer disk with additional openings in the area of at least one of the spring sections.
So that the largest possible openings in the spacer disk can be realized, the openings in the spacer disk and the cover surfaces in the switching disk extend in the circumferential direction.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.